They're too similar for me because of the sound and etymology. I also have a bit of a problem saying it, so we ruled it out for DS2. Though I now know a Rory who I see regularly and I find if I don't think about saying his name it seems to come out ok, at least no one has corrected or laughed at me, but I still feel uncomfortable saying it.

I had horrible times saying my 'r's as a child, and Rory would've come out as Woawee for most of elementary school if I said it. My one name came out as Waynie, but Rory would have been ten times worse.

But besides the troubles kids with speech impediments would have, Rory and Rowan are both unisex names that are two syllables and both start with Ro. They are tied to the color red, which I see as a plus for a hidden connection, but the combo sounds like a matchy-matchy sibset/twinset. I wouldn't do it. It's way too similar.

I think it's hard for some people to pronounce. I've always had a hard time with it. I love your daughters name, Rowan, though, and I think it's totally fine to have both of their names start with R. However, I do think Rory and Rowan are too similar.